Lead-free piezoelectric ceramic Bi 0.5 Na 0.5 TiO 3 (BNT) Magnesium oxide (MgO) Mixed oxide method This study investigates the effects of adding MgO and a sintering temperature on the microstructure, as well as the relative density of a disk of the lead-free piezoelectric ceramic of Bi 0.5 Na 0.5 TiO 3 doped with MgO (BNT-MgO), prepared using the mixed oxide method. Three kinds of starting powders (such as Bi 2 O 3 , Na 2 CO 3 and TiO 2 ) were mixed and calcined. This calcined BNT powder and a certain weight percentage of MgO were mixed, sintered, and compressed into a green compact of BNT-MgO. This green compact of BNT-MgO was sintered to be a disk doped with MgO, and its characteristics (such as density and microstructure) were measured. At a fixed wt.% of MgO, as the sintering temperature increased, the grain size of the disk increased, but the relative density of the disk decreased. The largest relative density of the disk obtained in this study was 98.0% at a sintering temperature of 1000 Β°C and with 1.0 wt.% of MgO. This study shows that adding MgO to the BNT not only improves the relative density of the disk, but it also lowers the sintering temperature.